1
Fernando Pozzi Semeghini Guastaldi
C
ARACTERIZAÇÃO FÍSICO-
QUÍMICA,
MORFOLÓGICA,
ANÁLISE MECÂNICA EDE ELEMENTOS FINITOS
3D,
DE DIFERENTES PLACAS E PARAFUSOSMETÁLICOS E TÉCNICAS DE FIXAÇÃO INTERNA
,
EMPREGADAS EMFRATURAS DE ÂNGULO MANDIBULAR
ARAÇATUBA
-
SP
2
Fernando Pozzi Semeghini Guastaldi
CARACTERIZAÇÃO FÍSICO-QUÍMICA, MORFOLÓGICA, ANÁLISE
MECÂNICA E DE ELEMENTOS FINITOS 3D, DE DIFERENTES PLACAS E
PARAFUSOS METÁLICOS E TÉCNICAS DE FIXAÇÃO INTERNA,
EMPREGADAS EM FRATURAS DE ÂNGULO MANDIBULAR.
ARAÇATUBA - SP
3
Fernando Pozzi Semeghini Guastaldi
CARACTERIZAÇÃO FÍSICO-QUÍMICA, MORFOLÓGICA, ANÁLISE
MECÂNICA E DE ELEMENTOS FINITOS 3D, DE DIFERENTES PLACAS E
PARAFUSOS METÁLICOS E TÉCNICAS DE FIXAÇÃO INTERNA,
EMPREGADAS EM FRATURAS DE ÂNGULO MANDIBULAR.
Tese apresentada à Faculdade de Odontologia do Câmpus
de Araçatuba - Universidade Estadual Paulista “Júlio de
Mesquita Filho” - UNESP, para obtenção do Tίtulo de DOUTOR EM ODONTOLOGIA - Área de Concentração em
Cirurgia e Traumatologia Buco-Maxilo-Facial.
Orientador: Prof. Adj. Eduardo Hochuli Vieira
ARAÇATUBA - SP
4
Ficha Catalográfica
Dados Internacionais de Catalogação na Publicação (CIP) Ficha catalográfica elaborada pela Biblioteca da FOA / UNESP
Guastaldi, Fernando Pozzi Semeghini.
G917 Caracterização físico-química, morfológica, análise mecânica e de elementos finitos 3D, de diferentes placas e parafusos metálicos e técnicas de fixação interna, empregadas em fraturas de ângulo mandibular.
Fernando Pozzi Semeghini Guastaldi. – Araçatuba : [s.n.], 2013
118 f. : il. ; tab. + 1 CD-ROM
Tese (Doutorado) – Universidade Estadual Paulista, Faculdade de Odontologia de Araçatuba
Orientador: Prof. Adj. Eduardo Hochuli Vieira
1. Análise de elementos finitos 2. Mandíbula 3. Fixação interna de fraturas 4. Titânio 5. Molibdênio I. T.
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Dados Curriculares
Fernando Pozzi Semeghini Guastaldi
NASCIMENTO: 22/03/1982 – São Carlos/SP FILIAÇÃO: Antônio Carlos Guastaldi
Norma Pozzi Semeghini
1999/2000: Técnico em Prótese Dentária
Centro Integrado de Educação (CIESC) – São Carlos.
2003/2006: Curso de Graduação em Odontologia
Faculdade de Odontologia – Universidade de Ribeirão Preto – UNAERP.
2007/2007: Estágio no Departamento de Diagnóstico Oral na Área de Cirurgia
Bucomaxilofacial – FOP – UNICAMP.
2008/2010: Curso de Pós-Graduação em Cirurgia e Traumatologia Buco-Maxilo-Facial
6
2011: Título de Especialista em Cirurgia e Traumatologia Buco-Maxilo-Facial
concedido pelo Conselho Federal de Odontologia (CFO).
2010/2013: Curso de Pós-Graduação em Cirurgia e Traumatologia Buco-Maxilo-Facial
na Faculdade de Odontologia de Araçatuba – Unive sidade Estadual Paulista Júlio de Mes uita Filho – nível Doutorado.
2011/2011: Professor Substituto junto à Disciplina de Cirurgia e Traumatologia
Buco-Maxilo-Facial, FOA – UNESP.
2012/2012: Visiting Scholar e Research Scientist no Departament of Biomaterials and
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8
Aos meus pais,
Norma e Antônio Carlos
Pelo amor, carinho, paciência, dedicação e por todas as
vezes em que abdicaram de seus sonhos para a realização dos meus.
Admiro muito vocês por serem pais tão maravilhosos, que souberam me
educar com amor, apoio e com grandes atitudes.
Vocês são exemplos de vida para mim e espero que eu possa
retribuir pelo menos parte de todo o amor que dedicaram e que
continuam dedicando a mim. Tenho muito orgulho de ser filho de vocês!
9
Aos meus avós,
Adelina (in memoriam) e Moacir Guastaldi (in memoriam)
Haydée e Antônio Semeghini
Pelo amor, carinho, incentivo e dedi
cação que
sempre tiveram comigo.
Vocês são exemplos de carát
er,
honestidade e simplicidade.
Sinto muita falta de vocês, da
minha
infância, da nossa convivência.
Muito obrigado por
tudo que sempre fizeram e que ainda fazem por mim! Amo muito
vocês!
Ao meu primeiro e grande amigo Edinho (
in
memoriam
).
Exemplo
de
dignidade,
simplicidade
e
perseveran
ç
a. Voc
ê
se foi... Mas conosco ficam as boas
10
11
Ao meu orientador, Professor Dr. Eduardo Hochuli Vieira, grande
exemplo de competência, dedicação e dignidade. Obrigado pela
oportunidade oferecida, pelos preciosos ensinamentos, paciência,
incentivo constante, por ter acreditado em mim e me proporcionado à
realização de um grande sonho. Muito Obrigado!
Ao Professor Dr. Idelmo Rangel Garcia Júnior, pelo profissional
dedicado, seguro e competente. Pela disposição em sempre nos ensinar,
direcionar e incentivar. Você é e sempre será um grande exemplo de
competência, amor e dedicação à profissão. Obrigado pela paciência que
sempre demonstrou diante de minhas dúvidas, questionamentos e
angústias. Muito Obrigado!
Ao Professor Dr. Osvaldo Magro Filho, pela competência e
preciosos conhecimentos transmitidos. Obrigado pela amizade,
confiança, incentivo e por considerar os alunos da pós-graduação seus
verdadeiros amigos, sempre se preocupando conosco e dividindo inúmeros
momentos de alegria. Muito obrigado!
Ao Prof. Dr. Paulo Guilherme Coelho, que confiou no meu trabalho
e abriu as portas da New York University para que eu aprendesse novas
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13
À Faculdade de Odontologia de Araçatuba - UNESP, sob direção da
Professora Dra. Ana Maria Pires Souhbia e vice-direção do Professor
Dr. Wilson Roberto Poi pela oportunidade de realização do curso de
Doutorado!
Ao Programa de Pós-Graduação em Odontologia da Faculdade de
Odontologia de Araçatuba - UNESP, pela oportunidade de realização do
curso de Doutorado!
Aos meus familiares, que sempre torceram, apoiaram e me
incentivaram. Muito obrigado!
À minha querida prima Carolina e ao seu marido Carl Clarke, por
todo o carinho, receptividade, apoio, ajuda e por serem pessoas com
caráter, dignidade e simplicidade! Amo muito voces!
Aos amigos: Rodolfo Bruniera Anchieta, Lucas Machado Silveira,
Daniel Galera Bernabé e Juliana Aparecida Delben, pela convivência,
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Aos meus amigos, pela amizade, pelos momentos de alegria,
descontração, por serem exemplos de honestidade, lealdade e
companheirismo. Muito obrigado!
Aos amigos do curso de Mestrado e Doutorado em Cirurgia e
Traumatologia Buco-Maxilo-Facial, pelos momentos compartilhados, ajuda
e amizade!
Aos amigos da Pós-Graduação em Odontologia, pela ajuda,
agradável convivência e momentos compartilhados!
Aos alunos do Curso de Graduação da Faculdade de Odontologia de
Araçatuba - UNESP, pelo respeito, credibilidade e confiança
depositados aos alunos da Pós-Graduação!
Aos funcionários do Laboratório de Cirurgia, da Pós-Graduação e
da Biblioteca, pela paciência, disponibilidade e ajuda!
Ao Professor Eduardo Passos Rocha e seus orientados: Rodolfo,
Ana Paula e Gustavo, pela colaboração no desenvolvimento da análise de
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Aos Professores do Programa de Pós-Graduação em Odontologia da
Faculdade de Odontologia de Araçatuba por contribuírem para a minha
formação acadêmica!
Aos Professores Membros da Banca Examinadora da minha Tese de
Doutorado: Prof. Dr. Eduardo Hochuli Vieira, Prof. Dr. Idelmo Rangel
Garcia Junior, Prof. Dr. Luis Geraldo Vaz, Prof. Dr. Eduardo Sanches
Gonçales e Prof. Dr. Sérgio Alexandre Gehrke!
À Coordenação de Aperfeiçoame
nto de Pessoal de
Nível
Superior (CAPES), pela concessão da Bolsa de Estágio de
Doutorando no Exterior (Doutorado Sandwich; Processo BEX
8487/11-1). Obrigado por esse grande incentivo!
… à
todas as pessoas que, direta ou indiretamente,
í
este trabalho,
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17
É
lan
ç
ar-se em busca de conquistas
grandiosas, mesmo expondo-se ao fracasso, do que alinhar-se
í
, que nem gozam muito nem sofrem
muito, porque vivem numa penumbra cinzenta, onde
ã
conhecem
ó
,
.
Theodore Roosevelt
Q
a adversidade; mas,
se quiser colocar
à
á
,
ê
-
.
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19
Guastaldi, FPS. Caracterização fίsico-quίmica, morfológica, análise mecânica e
de elementos finitos 3D, de diferentes placas e parafusos metálicos e técnicas
de fixação interna, empregadas em fraturas de ângulo mandibular [Tese].
Araçatuba: Faculdade de Odontologia da Universidade Estadual Paulista; 2013.
Resumo Geral
Proposição: Realizar uma caracterização físico-química, morfológica e
comparar o comportamento mecânico de uma liga experimental de Ti-Mo, ao
sistema de fixação análogo à base de Ti, em fraturas de ângulo mandibular,
favoráveis ao deslocamento. Adicionalmente, análises de elementos finitos 3D
foram realizadas para avaliar o padrão de distribuição de tensões nas placas e
nos parafusos.
Material e Método: Vinte e oito réplicas de mandίbulas de poliuretano foram
usadas e uniformemente seccionadas na região do ângulo mandibular
esquerdo. Estas foram divididas em 4 grupos considerando o material das
placas e as técnicas de fixação interna: grupo Eng 1P, uma placa (zona de
tensão da mandίbula) e 4 parafusos de 6 mm de comprimento; grupo Eng 2P,
duas placas (uma na zona de tensão da mandίbula e a outra na zona de
compressão), a primeira fixada com 4 parafusos de 6 mm de comprimento e a
segunda com 4 parafusos de 12 mm de comprimento, sendo todo o material de
fixação do sistema 2.0-mm. Os mesmos grupos foram criados para a liga
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As médias e os desvios-padrão foram comparados para avaliação estatίstica
(ANOVA; p < .05). Adicionalmente, foi construído um modelo de elementos
finitos 3D considerando as mesmas variáveis para avaliar as tensões
equivalentes de von Mises (σvM) nas placas e nos parafusos.
Resultados: Diferença estatisticamente significativa (p < .05) foi encontrada
quando foi realizada a comparação entre ambas as técnicas de fixação (1 e 2
placas), independentemente do material das placas (cpTi and Ti-15Mo).
Quando considerado os valores das tensões equivalentes de von Mises (σvM)
para a comparação entre ambos os grupos (Eng and Ti-15Mo) com 1 placa,
verificou-se uma redução de 10.5% na placa e de 29.0% nos parafusos, para o
grupo da liga titânio-molibdênio. Ainda, quando foi realizada a comparação dos
mesmos grupos com 2 placas, o fator mais relevante foi uma redução, na
concentração das tensões, de 28.5% nos parafusos para o grupo Ti-15Mo.
Conclusão: A técnica de fixação com 2P mostrou melhor comportamento
mecânico em fraturas de ângulo mandibular, favoráveis ao deslocamento,
considerando ambos os materiais utilizados, Ticp e Ti-15Mo, quando
submetidos a uma carga vertical linear na região de molar. As placas de
titânio-molibdênio reduziram, substancialmente, as concentrações de tensões nos
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Guastaldi FPS. Physico-chemical and morphological characterization,
mechanical and 3D finite element analysis, of different metal plates and screws
and internal fixation techniques, employed in mandibular angle fractures
[Thesis]. Araçatuba: School of Dentistry of Sao Paulo State University; 2013.
General Abstract
Purpose: Perform a physico-chemical and morphological characterization and
compare the mechanical behavior of an experimental Ti-Mo alloy to the
analogous metallic Ti-based fixation system, for mandibular angle fractures,
favorable to displacement. Additionally, finite element analysis was performed
to assess the stress distribution in the plates and screws.
Material and Method: Twenty eight polyurethane mandible replicas were used
and uniformly sectioned on the left mandibular angle. These were divided into 4
groups considering the material of the plates and the internal fixation
techniques: group Eng 1P, one 2.0-mm plate (tension zone of the mandible)
and 4 screws 6 mm long; group Eng 2P, two 2.0-mm plates (one in the tension
zone of the mandible and the other in the compression zone), the first fixed with
4 screws 6 mm long and the second with 4 screws 12 mm long. The same
groups were created for the titanium alloy (Ti-15Mo). Each group was subjected
to linear vertical loading at the first molar. Means and standard deviations were
compared with respect to statistical significance (ANOVA; p < .05). Additionally,
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specimens used in the mechanical tests were created to evaluate the von Mises
equivalent stress (σvM) in the plates and screws.
Results: Statistically significant difference (p < .05) was found when the
comparison between both internal fixation techniques (1 and 2 plates) was
performed, regardless the materials of the plates (cpTi and Ti-15Mo). When
considering the von Mises equivalent stress (σvM) values for the comparison
between both groups (Eng and Ti-15Mo) with 1 plate, an decrease of 10.5% in
the plate and an decrease of 29.0% in the screws for the
titanium-molybdenum-based group was observed. Also, when comparing the same groups with 2
plates, the relevant fact was an decrease of 28.5% in the screws for the
Ti-15Mo group.
Conclusion: The 2P technique showed better mechanical behavior for
favorable to displacement angle fracture fixation than 1P, considering both
materials, cpTi and Ti-15Mo, of the bone plates when the fixation methods were
subjected to linear vertical loading in the molar region. The
titanium-molybdenum alloy plates substantially decreased the stress concentration in the
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Lista de Figuras
Capitulo 1
Figure 1 The location of the titanium-based system for both internal
fixation techniques, (a) 1 plate and (b) 2 plates.
Figure 2 The location of the titanium-molybdenum-based system for
both internal fixation techniques, (a) 1 plate and (b) 2 plates.
Figure 3 Vertical linear load applied at the 1st inferior molar, during
the mechanical test on a servo-hydraulic machine.
Figure 4 SEM micrograph of Ti-15Mo alloy sample; (a) Mo mapping
(white points) and (b) Ti mapping (white points) of the Ti-15Mo alloy
sample. Magnification 2.000X.
Figure 5 Optical microscopy of the plates, after the surface attack
with Kroll solution, revealing the microstructures of the (a) cpTi and the
(b) Ti-15Mo alloy. Magnification 500X.
Figure 6 SEM micrograph showing the screw (Ti6Al4V) morphology;
(a) screw tip and (b) screw thread. Magnification 200X.
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63
64
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Figure 7 (top) SEM micrograph showing the plates (Engimplan e
Ti-15Mo) morphology (plate thread); (bottom) EDX of the same surfaces.
Magnification 500X.
Figure 8 Mean and standard deviation (SD) of the results obtained in
the biomechanical analysis, considering the material of the bone plates
and the internal fixation technique employed (two-factor factorial
ANOVA).
Capitulo 2
Figure 1 Synthetic mandible before the CT scan.
Figure 2 Geometric model of the mandibular segment (Mimics 13.1)
involving only part of the body (with the 1st and 2nd molars), the lower half
of the ramus and the mandibular angle.
Figure 3 Reconstruction of the mandible segment (SolidWorks 2010)
simulating the fracture in the mandibular angle.
Figure 4 Geometric models of the plate and the screws (SolidWorks
2010).
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68
93
94
95
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Figure 5 Meshed model showing the 2 plate configurations analyzed
in the study: (left) 4-hole monocortical tension band plate at the superior
border, and (right) 4-hole monocortical tension band plate and 4-hole
bicortical compression band plate at the inferior border.
Figure 6 Stress distributions in the mandibular model by a 100 N
vertical load. Stress was mainly located around the loading region (1st
molar).
Figure 7 Group Eng 1P: von Mises equivalent stress (σvM) for the (a)
plate and (b) the screws.
Figure 8 Group Ti-15Mo 1P: von Mises equivalent stress (σvM) for
the (a) plate and (b) the screws.
Figure 9 Group Eng 2P: von Mises equivalent stress (σvM) for the (a)
plates and (b) the screws.
Figure 10 Group Ti-15Mo 2P: von Mises equivalent stress (σvM) for
the (a) plates and (b) the screws.
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98
99
100
101
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Lista de Tabelas
Capitulo 1
Table 1 Chemical analysis for Ti-15Mo alloy ingots (wt %).
Table 2 Mean and standard deviation (SD) of the loads obtained
during the mechanical test, for all groups.
Capitulo 2
Table 1 Mechanical properties (Elasticity modulus and Poisson's
ratio) of the materials.
Table 2 Von Mises (MPa) equivalent stress (σvM) values.
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104
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Lista de Abreviaturas
AEF Análise de Elementos Finitos
Ti Titanium
Mo Molybdenum
EDXRF Energy Dispersive X-ray Fluorescence
EDX Energy Dispersive X-ray
wt % Weight Percent
SEM Scanning Electron Microscopy
cpTi Comercially Pure Titanium
Ti-Mo Titanium Molybdenum
® Trademark
Ti-15Mo Titanium 15% Molybdenum
ASTM American Society for Testing and Materials
Ti6Al4V Titanium 6% Aluminium 4% Vanadium
IQAr Instituto de Quίmica de Araraquara
UNESP Universidade Estadual Paulista “Júlio de Mesquita Filho”
Eng Engimplan®
1P One Plate
mm Millimeter
2P Two Plates
MTS Material Test System
mm/min Millimiter per Minute
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SD Standard Deviation
% Percent Sign
Co Cobalt
Cr Chromium
SS Stainless Steel
FEA Finite Element Analysis
3D Three-Dimensional
CT Computed Tomography
1st First
2nd Second
.igs Initial Graphics Exchange Specification
σvM Von Mises Equivalent Stress
n Significance
MPa Megapascal
GPa Gigapascal
ELI Extra-Low Interstitial
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Sumário
Introdução Geral
1. Capítulo 1 Biomechanical study in polyurethane mandibles of different metal plates and internal fixation techniques, employed in mandibular angle fractures
1.1 Abstract 1.2 Introduction
1.3 Material and Method 1.4 Results 1.5 Discussion 1.6 Conclusion 1.7 References 1.8 Figures 1.9 Tables
2. Capítulo 2 3D FEA of the stress distribution within different metal plates and screws and internal fixation techniques, in mandibular angle fractures
2.1 Abstract
32
2.5 Discussion 2.6 Conclusion 2.7 References 2.8 Figures 2.9 Tables
Anexos
Anexo A Normas do periódico Journal of Craniofacial Surgery (JCS), selecionado para a publicação do Capítulo 1.
Anexo B Normas do periódico International Journal of Oral and Maxillofacial Surgery (IJOMS), selecionado para a
publicação do Capítulo 2.
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107
108
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Introdução Geral
As fraturas mandibulares constituem o tipo de trauma mais comum do
esqueleto facial. Os relatos demonstram uma proporção de 6:2:1 entre as
fraturas de mandίbula, do zigoma e da maxilla (Haug et al., 1990). O principal
objetivo no tratamento das fraturas é o reparo do osso fraturado resultando no
restabelecimento da forma e função. O controle do risco de infecção, da
má-união e de lesões dos tecidos moles, são alguns dos desafios técnicos que
podem ser incluídos no manejo global dos traumatismos (Laughlin et al., 2007).
Dentre as fraturas mandibulares, as da região de ângulo apresentam alta
incidência, sendo uma das mais frequentes na atualidade e sua gravidade está
diretamente relacionada ao tipo de trauma que as ocasionou (Ellis 3rd, 2009).
O ângulo mandibular foi definido, anatomicamente, por uma região triangular,
delimitada pela borda anterior do músculo masseter e uma linha oblíqua, que
se estende da região do terceiro molar inferior à inserção posterior do músculo
masseter (Killey, 1974). De acordo com Ellis 3rd et al. (1985), elas
representavam 10% das fraturas mandibulares em pacientes vítimas de
acidentes automobilísticos, 17% em pacientes vítimas de quedas, podendo
representar até 30% das fraturas mandibulares em pacientes vítimas de
agressão física.
Esse tipo de diversidade não ocorre em relação ao perfil dos pacientes
que apresentam fratura do ângulo mandibular. Em sua grande maioria, são
indivíduos do gênero masculino, economicamente ativos e na faixa etária de 20
à 40 anos (Ellis 3rd et al., 1985; Lee & Dodson, 2000; Gabrielli et al., 2003;
35
Quanto à modalidade de tratamento a ser empregada, as fraturas de
ângulo mandibular apresentam diversas formas de condução, sendo grande
foco de controvérsias, talvez sendo superadas somente para as da região de
côndilo mandibular. Controvérsias essas muito mais relacionadas a fatores
ligados à preferência e/ou experiência do profissional responsável pela
condução do caso, do que com base científica (Ellis 3rd, 1999, 2009). A fixação
interna tem sido empregada com sucesso no tratamento das fraturas
mandibulares durante as últimas décadas (Siddiqui et al., 2007) de acordo com
os princípios estabelecidos por Michelet et al. (1973) e Champy et al. (1978).
Diversas formas de tratamento são propostas para as fraturas de ângulo
mandibular, como por acesso intrabucal e aplicação de uma placa na linha
oblíqua externa (Michelet et al., 1973; Champy et al., 1978), ou por acesso
transbucal e aplicação de duas placas, ou ainda, acesso extrabucal e aplicação
de duas placas. A primeira forma de tratamento citada destaca-se por ser
tecnicamente mais simples e rápida, por evitar o risco de lesão ao nervo facial
e à possibilidade de cicatriz aparente (Edwards & David, 1996).
Assim, para melhor compreensão do comportamento biomecânico da
fixação interna das fraturas mandibulares, e para possibilitar o desenvolvimento
de novos materiais e técnicas, foram realizados estudos experimentais in vitro
(Haug et al., 2002; Rudderman et al., 2008). Estes estudos necessitam da
utilização de osso humano ou de um substituto ósseo. Vários materiais, como
costela bovina, mandíbulas de ovelhas, réplicas de mandíbulas humanas em
resina de poliuretano, têm sido utilizados como substitutos ósseos em pesquisa
36
As placas e parafusos de titânio constituem-se no padrão ouro para a
fixação de fraturas bucomaxilofaciais e sua utilização em trauma têm sido
amplamente estudada (Bell & Kindsfater, 2006). Laughlin et al. (2007),
reportaram que a escolha do tipo de fixação interna para as fraturas de
mandíbula deve apresentar as seguintes características: simplicidade de
instalação, apropriada resistência mecânica para suportar os esforços
mastigatórios e o adequado treinamento e conhecimento, por parte do
profissional, do sistema utilizado.
Ainda, a realização de pesquisas in vitro, in vivo, para o estudo e o
desenvolvimento de diferentes materiais empregados na fabricação das placas
e parafusos, das diferentes técnicas utilizadas como fixação interna,
empregados no tratamento das fraturas e osteotomias da face, são
imprescindíveis para avaliar o comportamento mecânico, a resposta biológica,
local e sistêmica, que este biomaterial poderá desencadear ao receptor para,
posteriormente, tornar possível sua aplicação em humanos.
Desta forma, para melhor compreensão do comportamento dos
diferentes materiais e técnicas empregados nos traumas bucomaxilofaciais, a
utilização de modelos matemáticos virtuais associados à simulação numérica
empregando-se análise de elementos finitos (AEF) tem demonstrado ser um
meio de prever a distribuição e concentração de tensões e deslocamentos em
áreas fraturadas que necessitam de fixações (Takada et al., 2006; Wang et al.,
2010; Ji et al., 2010; Takahashi et al., 2010).
É possível afirmar que a AEF é um método preciso para se avaliar o
comportamento mecânico de estruturas, desde que as propriedades mecânicas
37
(Vollmer et al., 2000). Com o auxílio da AEF, pode-se aprimorar a técnica
cirúrgica, estimulando o desenvolvimento de novos biomateriais, através de
simulações que representem diferentes formas de fratura do ângulo
mandibular, com diferentes materiais e quantidade de parafusos, com o
objetivo de reduzir a concentração de tensões na área fraturada, auxiliando
38
Referências
1. Bell RB & Kindsfater CS. The use of biodegradable plates and screws to
stabilize facial fractures. J Oral Maxillofac Surg 2006;64:31-9.
2. Bredbenner TL & Haug RH. Substitutes for human cadaveric bone in
maxillofacial rigid fixation research. Oral Surg Oral Med Oral Pathol Oral Radiol
Endod 2000;90:574-80.
3. Champy M, Lodde JP, Schmitt R, Jaeger JH, Muster D. Mandibular
osteosynthesis by miniature screwed plates via a buccal approach. J Oral
Maxillofac Surg 1978;6:14-21.
4. de Matos FP, Arnez MFM, Sverzut CE, Trivellato AE. A retrospective study of
mandibular fracture in a 40-month period. J Oral Maxillofac Surg 2010;39:10-5.
5. Edwards T & David D. A comparative study of miniplates used in the treatment
of mandibular fractures. Plast Reconstr Surg 1996;97:1150-6.
6. Ellis E 3rd, Moos KF, el-Attar A. Ten years of mandibular fractures: an analysis
of 2,137 cases. Oral Surg Oral Med Oral Pathol 1985;59:120-9.
7. Ellis E 3rd. Treatment methods for fractures of the mandibular angle. Int J Oral
Maxillofac Surg 1999;28:243-52.
8. Ellis E 3rd. Management of fractures through the angle of the mandible. Oral
Maxillofac Surg Clin North Am 2009;21:163-74.
9. Gabrielli MAC, Gabrielli MFR, Marcantonio E, Hochuli-Vieira E. Fixation of
mandibular fractures with 2.0-mm miniplates: Review of 191 cases. J Oral
Maxillofac Surg 2003;61:430-6.
10. Haug RH, Prather J, Indresano AT. An epidemiologic survey of facial fractures
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11. Haug RH, Street CC, Goltz M. Does plate adaptation affect stability? A
biomechanical comparison of locking and nonlocking plates. J Oral Maxillofac
Surg 2002;60:1319-26.
12. Ji B, Wang C, Liu L, Long J, Tian W, Wang. A biomechanical analysis of
titanium miniplates used for treatment of mandibular symphyseal fractures with
the finite element method. Oral Surg Oral Med Oral Pathol Oral Radiol Endod
2010;109:e21-7.
13. Killey HC. Fractures of the mandible. Bristol: Wright. 2nd ed. 1974. 13p. Apud
Banks P. Killey’s - Fraturas de Mandíbula. São Paulo: Santos. 4a ed. 1994. 15p. 14. Laughlin RM, Block MS, Wilk R, Malloy RB, KentJN. Resorbable plates for the
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2007;65:89-96.
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plates in maxillofacial surgery. J Oral Maxillofac Surg 1973;1:79-84.
17. Paza AO, Abuabara A, Passeri LA. Analysis of 115 mandibular angle fractures.
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18. Rudderman RH, Mullen RL, Phillips JH. The biophysics of mandibular fractures:
an evolution toward understanding. Plast Reconstr Surg 2008;121:596-607.
19. Siddiqui A, Markose G, Moos KF, McMahon J, Ayoub AF. One miniplate versus
two in the management of mandibular angle fractures: a prospective
randomised study. Br J Oral Maxillofac Surg 2007;45:223-5.
20. Takada H, Abe S, Tamatsu Y, Mitarashi S, Saka H, Ide Y. Three-dimensional
bone microstructures of the mandibular angle using micro-CT and finite element
analysis: relationship between partially impacted mandibular third molars and
40
21. Takahashi H, Moriyama S, Furuta H, Matsunaga H, Sakamoto, Y, Kikuta T.
Three lateral osteotomy designs for bilateral sagittal split osteotomy:
biomechanical evaluation with three-dimensional finite element analysis. Head
Face Med 2010;26;6:4.
22. Vollmer D, Meyer U, Joos U, Vègh A, Piffko J. Experimental and finite element
study of a human mandible. J Craniomaxillofac Surg 2000;28(2):91-6.
23. Wang H, Ji B, Jiang W, Liu L, Zhang P, Tang W, Tian W, Fan Y.
Three-dimensional finite element analysis of mechanical stress in symphyseal
fractured human mandible reduced with miniplates during mastication. J Oral
41
42
1. Capítulo 1
B
IOMECHANICAL STUDY IN POLYURETHANE MANDIBLES OF DIFFERENTMETAL PLATES AND INTERNAL FIXATION TECHNIQUES
,
EMPLOYED IN MANDIBULAR ANGLE FRACTURES
43
1.1 Abstract
Purpose: Perform a physico-chemical and morphological characterization and
compare the mechanical behavior of an experimental Ti-Mo alloy to the
analogous metallic Ti-based fixation system, for mandibular angle fractures,
favorable to displacement.
Material and Method: Twenty eight polyurethane mandible replicas were used
and uniformly sectioned on the left mandibular angle. These were divided into 4
groups considering the material of the plates and the internal fixation
techniques: group Eng 1P, one 2.0-mm plate (tension zone of the mandible)
and 4 screws 6 mm long; group Eng 2P, two 2.0-mm plates (one in the tension
zone of the mandible and the other in the compression zone), the first fixed with
4 screws 6 mm long and the second with 4 screws 12 mm long. The same
groups were created for the titanium alloy (Ti-15Mo). Each group was subjected
to linear vertical loading at the first molar on the plated side in an MTS-810
servo-hydraulic mechanical testing unit. The maximum load resistance values
were measured. Means and standard deviations were compared with respect to
statistical significance using the two-factor factorial analysis of variance
(ANOVA; p < .05).
Results: The chemical composition of the Ti-15Mo alloy was close to the
nominal value in all cases. The mapping of Mo and Ti showed a homogeneous
distribution of these elements. SEM of the screw, revealed the presence of
44
treatment. The metallographic analysis reveals granular microstructure, from
the thermomechanical trials. No statistically significant difference (p > .05) was
found when the materials of the plates (cpTi and Ti-15Mo) where considered for
both techniques of fixation (1 and 2 plates). However, when the comparison
between both internal fixation techniques was performed, statistically significant
difference was found (p < .05).
Conclusion: The 2P technique showed better mechanical behavior for
favorable to displacement angle fracture fixation than 1P, considering both
materials, cpTi and Ti-15Mo, of the bone plates when the fixation methods were
subjected to linear vertical loading in the molar region.
Keywords: Mandible; fracture fixation, internal; bone plates; titanium;
45
1.2 Introduction
Mandible fractures are among the most common injuries that affect the
facial skeleton (Ellis et al., 1985; Haug et al., 1990). Moreover, fractures of the
mandibular angle are the most problematic in the facial region because of the
high frequency of complications and difficult surgical access to the site (Gear et
al., 2005; Fernandez et al., 2003; Haug et al., 2001).
Infection and non-union are commonly reported after rigid internal fixation
of these fractures (Mathog et al., 2000). Despite significant research on the
subject, there is still some controversy on the ideal fixation scheme for fractures
of this region (Gear et al., 2005; Kimsal et al., 2011). Treatment of mandibular
fractures is based on the restoration of form and function, seeking suitable bone
repair. The basic requirement for optimal function is adequate anatomic shape
and stiffness (resistance to deformation under load) (Prein & Rahn, 1998).
After a fracture, the transmission of compressive forces can still take
place across a fracture plane. The bone remains able to take over the
compressive tasks, and the implant must substitute for the lost tensile
properties. For more than 2 decades, open reduction with stable internal fixation
has been the treatment of choice for mandibular fractures. Correct implant
placement is determined by the location and type of fracture and its relation to
the tension zones (Prein & Rahn, 1998).
Rigid internal fixation is now routinely used for surgical management of
mandible fractures (Feller et al., 2002; Moreno et al., 2000; Fernandez et al.,
2003; Dolanmaz et al., 2004). Mandible stability during functional activities
46
strong and rigid enough to withstand the functional loads and enable
undisturbed fracture healing. Therefore, optimized internal fixation should attain
a balance between the stability of the fragments and the stress shield effect of
the miniplates (Ji et al., 2010).
Fixation methods can be evaluated empirically by mechanical tests using
universal testing machines. Samples made with material that has a modulus of
elasticity similar to that of bone are duly prepared to simulate fracture fixation.
Thus, it is possible to observe the trend of the fixation system behavior when
exposed to load (Vieira e Oliveira & Passeri, 2011).
The aim of this study was to perform a physicochemical and
morphological characterization and a comparative evaluation of the mechanical
behavior of an experimental Ti-Mo alloy to the analogous metallic Ti-based
47
1.3 Material and Method
Prior to the mechanical test, Energy Dispersive X-ray Fluorescence
(EDXRF) and Energy Dispersive X-ray (EDX) spectra were used to confirm that
the ingots composition was close to nominal (15Mo wt%). The chemical
analyses were performed in a total of six different areas on the bulk and on the
surface of each ingot by both techniques (EDXRF and EDX).
After chemical characterization, metallographic observation with
Scanning Electron Microscopy (SEM) and mapping of Mo were performed on
the samples’ surface in order to verify possible defects from casting process
and the distribution of Mo. The experiments were conducted using a SEM
microscope (LEO 440, LEO Electron Microscopy Ltd., Cambridge, UK) coupled
with an energy dispersive analyzer, while for EDXRF measurements, a
fluorescence X-ray spectrometer (EDX-800 RayNy, Shimadzu, Kyoto, Japan)
was used.
Also, an Optical Microscope (Leica DMR, Leica Microsystems, Wetzlar,
Germany) coupled with Leica Qwin Software was used to capture and analyze
the images of the microstructure of the cpTi and Ti-Mo alloy, after the surface
attack with Kroll solution (5% Nitric acid, 10% hydrofluoric acid and 85% volume
of water; ASTM E 407), to reveal its microstructure.
For this study, 28 human dentate mandibular replicas made of rigid
polyurethane resin (Nacional®, Jaú, SP, Brazil), were used as substrate. The
2.0-mm titanium-based system group consisted of 21 straight 4-hole plates with
48
(Engimplan®, Rio Claro, SP, Brazil). The 2.0-mm titanium-molybdenum-based
system group consisted of 21 straight 4-hole plates (Ti-15Mo).
Note: In accordance with the manufacturer's specifications, the plates are made of cpTi grade 2 (ASTM F67-06) and the screws are made of the titanium alloy Ti-6Al-4V
(ASTM F136-12a).
The titanium alloy (Ti-15Mo; ASTM F2066-08) used in this study, and
developed by the Biomaterials Group (IQAr - UNESP), to be applied as
biomaterials (Oliveira et al., 2004, 2007, 2008, 2009), was cast in an arc-melting
furnace under ultrapure argon atmosphere, following a well-known procedure
described in the literature (Oliveira et al., 2004, 2007). The ingots obtained after
the fusion of the elements (Ti and Mo), and after thermo-mechanical treatments,
were sent to Engimplan®, to be laminated into plates for internal fixation.
Before the study, a mandible was sectioned simulating a simple
mandibular angle fracture, favorable to displacement, following a procedure
described in the literature (Bregagnolo et al., 2011). Subsequently, the
sectioned mandible was sent to National® (Jaú, SP, Brazil) for reproducing the
standardized cut.
The samples were divided into 4 groups, with 7 mandibles each,
according to the plate material and internal fixation technique employed, as
described:
- Group Eng 1P was fixed with 1 straight 4-hole plate and 4 monocortical
49
- Group Eng 2P was fixed with 2 straight 4-hole plates, one in the tension
zone of the mandible and the other in the compression zone, the first
was fixed with 4 monocortical screws 6 mm long and the second with 4
bicortical screws 12 mm long (Figure 1);
The same groups were created for the titanium alloy (Ti-15Mo; Figure 2).
To standardize the position of the plates and the screw insertion, guides
of acrylic resin were made.
The mechanical test was performed on a servo-hydraulic machine
MTS-810 (Material Test System). Two steel devices were made and set up on the
MTS machine, one as a supporter to stabilize the mandible replicas and another
as a tip to apply the vertical loads (Figure 3). The force was applied through the
tip perpendicular to the occlusal plane at a rate of 1 mm/min at the first molar on
the plated side.
The data from the load, in Newtons (N), applied during the mechanical
test, was determined at the time at which the fixation failed.
The statistical analysis of the data obtained in the mechanical tests, were
compared using ANOVA, with two factors of variation (the plate material and
50
1.4 Results
The chemical analysis (EDXRF and EDX) showed that the actual
chemical composition of the Ti-15Mo alloy was close to the nominal value in all
cases (Table 1). The chemical composition of the alloy was homogeneous, and
no expressive differences were found between surface and bulk with both
techniques used (p > .10). The mapping of Mo and Ti showed a homogeneous
distribution of these elements, without preferential zone, in the whole analyzed
region (Figure 4).
Figure 5 shows the SEM of the screw (Ti-6Al-4V). Machining debris can
be seen, what is undesirable for in vivo application, while Figure 6 shows the
SEM of both plates. The cpTi plate undergoes a surface treatment not disclosed
by the company, while the Ti-15Mo plate does not present treatment.
The Optical Microscopy of the cpTi and the Ti-15Mo alloy is shown in
Figure 7. The metallographic analysis reveals granular microstructure, from the
thermomechanical trials, performed in its gross structure of fusion during the
manufacturing process. These trials are needed to show that these materials
have adequate mechanical resistance for application.
During the mechanical tests no fractures of the synthetic mandibles, of
the plates and the screws were detected. Table 2 shows the mean and
standard deviation (SD) values relative to the maximum forces (N) obtained
during the mechanical tests for all groups of the study.
No statistically significant difference (p > .05) was found when the
materials of the plates (cpTi and Ti-15Mo) where considered for both
51
when the comparison between both internal fixation techniques (1P and 2P)
52
1.5 Discussion
There have been many scientific researches that have studied the
behavior of fixation techniques in the mandible region when subjected to
mechanical tests, to confirm or support the best position, orientation, and
selection of plate type and materials employed in mandibular angle fracture
treatment. It is essential to understand the biomechanical behaviour of mandible
and optimize the fixation pattern to enable surgeons to improve the outcomes of
internal fixation (Dichard and Klotch, 1994; Choi et al., 1995a, 1995b; Shetty et
al., 1995; Haug et al., 1996; Fedok et al., 1998; Alkan et al., 2007; Ji et al.,
2012).
In 2000, Bredbenner & Haug compared human cadaver mandibular
bone, bovine rib, porcine rib, photoelastic epoxy, and two types of polyurethane
synthetic mandibles, each of which had been used previously in maxillofacial
biomechanical research. The mechanical standards for comparison were pullout
strength and insertional torque. They concluded that the polyurethane mandible
showed results similar to cadaveric bone and was considered by the authors to
be the material of choice for in vitro studies. Eliminating many of the variables
associated with natural or live tissue, permits a unique opportunity to assess
only the reconstruction technique and its mechanical interaction with the
substrate being reconstructed.
However, it is important to emphasize that the data obtained from
biomechanical studies, such as those used in the present study, can not be
directly transferred to clinical use in humans serving only as indicative
53
The introduction of modern devices for internal fixation substantially
shortens the duration of intermaxillary fixation or even obviates it completely.
One of the therapeutic goals of this kind of operation is to achieve
uncomplicated bone healing, so as to prevent any relapse. The plate/screw
osteosynthesis is a standard method for the surgical treatment of mandible
fractures nowadays (Levy et al., 1991; Mathog et al., 2000; Feller et al., 2002;
Arbag et al., 2008).
Models used in previous studies usually employ incisal edge loading or
molar loading to simulate the force involved in mastication (Kroon et al., 1991;
Dichard and Klotch, 1994; Choi et al., 1995a, 1995b; Shetty et al., 1995; Haug
et al., 1996; Fedok et al., 1998; Alkan et al., 2007; Ji et al., 2012). In this study,
a compressive load was applied to the occlusal surface of the mandibular 1st
molar on the plated side perpendibular to the occlusal plane, which has been
shown to exhibits the largest muscle recruitment activity (Lovald et al., 2009).
We agree that these models may lead to results not according with
physical conditions, however, they can predict the behavior of different
scenarios of internal fixation, with several fracture patterns, and the behavior of
the most common materials used in fabrication of the bone plates and screws.
The fixation of fractures of the mandibular angle is possibly more critical
than fixation of fractures located in other regions of the mandible. Fractures of
the angle are associated with the highest rate of postoperative complications of
all mandibular fractures (Iizuka et al., 1991; Ellis 3rd, 1999; Esen et al., 2012),
which might be related to the use of different techniques of fixation (Ellis 3rd,
1999). The preferred type of fixation is still controversial (Ellis 3rd, 1999; Levy et
54
the determination of best positioning, orientation, and selection of plate type and
material are important.
Although most of the studies indicate increase stiffness and strength in
multiple plate systems repair versus single-plate applications, much debate
exists about the use of either one or two plates for treating angle fractures. The
most common surgical treatment for angle fractures is the use of a single
miniplate with or without maxillo-mandibular fixation (Gear et al., 2005), with the
next most common being the two-miniplate technique. However, all
biomechanical models developed to date have shown that two plates provide
much more stability than one (Kroon et al., 1991; Dichard and Klotch, 1994;
Choi et al., 1995a, 1995b; Shetty et al., 1995; Haug et al., 1996; Fedok et al.,
1998; Alkan et al., 2007; Ji et al., 2012). Our results corroborates with the
literature and support the contention that the use of 2 plates when treating
simple fractures of the mandibular angle, unfavorable for treatment, with internal
fixation is superior to the use of 1 plate.
More, even if no statistically significant difference was found when the
comparison between the materials of the plates was performed, for both 1P and
2P, considering only the technique with 1 plate, there is a higher mechanical
resistance of the titanium-molybdenum alloy. This can be explained by the fact
that both, cpTi and Ti-15Mo, present different metallurgical structures what
implies in distinct deformation processes. Probably, when the cpTi plate enters
the permanent deformation process (plastic deformation), the Ti-15Mo plate still
is in the elastic deformation process.
Also, it is important to point out that the combined use of cpTi (bone plate
55
because they are different metals with different electrochemical potentials (Silva
et al., 1990). Thereby, the ideal scenario is to use the same material for the
manufacture of the plates and screws.
More, the literature showed that the vanadium (V) and aluminum (Al)
release in the Ti-6Al-4V alloy could induce Alzheimer’s disease, allergic
reaction, and neurological disorders (Mark & Waqar, 2007). Therefore, the
development of titanium alloys targeted for biomedical applications are highly
required, fact that corroborate with this study, once the
titanium-molybdenum-based alloy used, as published elsewhere (Oliveira et al., 2007, 2011), is
56
1.6 Conclusion
According to the methodology used and based in the results obtained, it
can be concluded that the fixation of a linear fracture of the mandibular angle,
favorable to displacement, is more resistant to mechanical testing when fixed
with the 2 plates technique. Moreover, we suggest that the plates and screws
be made of the same material.
Acknowledgements
The authors are thankful to Engimplan® (Rio Claro, SP, Brazil) for their support.
57
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9. Ellis E 3rd, Moos KF, el-Attar A. Ten years of mandibular fractures: an
analysis of 2,137 cases. Oral Surg Oral Med Oral Pathol 1985;59:120-9.
10. Ellis E 3rd. Treatment methods for fractures of the mandibular angle. Int J
Oral Maxillofac Surg 1999;28:243-52.
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noncompression miniplates in mandibular angle fractures: an experimental
study. Br J Oral Maxillofac Surg 2012;50:65-8.
12. Fedok FG, Van Kooten DW, DeJoseph LM, McGinn JD, Sobota B, Levin
RJ, Jacobs CR. Plating techniques and plate orientation in repair of
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13. Feller KU, Richter G, Schneider M, Eckelt U. Combination of microplate and
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15. Gear AJ, Apasova E, Schmitz JP, Schubert W. Treatment modalities for
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17. Haug RH, Barber JE, Reifeis R. A comparison of mandibular angle fracture
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18. Haug RH, Fattahi TT, Goltz M. A biomechanical evaluation of mandibular
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19. Iizuka T, Lindqvist C, Hallikainen D, Paukku P. Infection after rigid internal
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titanium miniplates used for treatment of mandibular symphyseal fractures
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21. Ji B, Wang C, Song F, Chen M, Wang H. A new biomechanical model for
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61
62
1.8 Figures
Figure 1. The location of the titanium-based system for both internal fixation
techniques, (a) 1 plate and (b) 2 plates.
a
63
Figure 2. The location of the titanium-molybdenum-based system for both
internal fixation techniques, (a) 1 plate and (b) 2 plates.
a
64
Figure 3. Vertical linear load applied at the first inferior molar, during the
65
Figure 4. SEM micrograph of Ti-15Mo alloy sample; (a) Mo mapping (white
points) and (b) Ti mapping (white points) of the Ti-15Mo alloy sample.
Magnification 2.000X.
a
66
Figure 5. Optical microscopy of the plates, after the surface attack with Kroll
solution, revealing the microstructures of the (a) cpTi and the (b) Ti-15Mo alloy.
Magnification 500X.
cpTi
Ti-15Mo
a
67
Figure 6. SEM micrograph showing the screw (Ti-6Al-4V) morphology; (a)
screw tip and (b) screw thread. Magnification 200X.
a
68
Figure 7. (top) SEM micrograph showing the plates (Engimplan e Ti-15Mo)
morphology (plate thread); (bottom) EDX of the same surfaces. Magnification
69
Figure 8. Mean and standard deviation (SD) of the results obtained in the
biomechanical analysis, considering the material of the bone plates and the
internal fixation technique employed (two-factor factorial ANOVA).
0 10 20 30 40 50 60 70 80
1 plate 2 plates
L o a d
(
N
)
Groups
Mean ± SD
Engimplan
70
71
1.9 Tables
Table 1 - Chemical analysis for Ti-15Mo alloy ingots (wt %).
Surface
Mean ± SD
Bulk
Mean ± SD
p value*
EDX
15.13 ± 0.25 15.11 ± 0.26
> .9999
EDXRF
14.86 ± 0.19 15.14 ± 0.32
.2499
72
Table 2 - Mean and Standard Deviation (SD) of the loads obtained during the
mechanical test, for all groups.
GROUPS
Engimplan
Ti-15Mo
1 plate
2 plates
1 plate
2 plates
Mean
20.80 N
59.40 N
26.60 N
56.50 N
73
74
2. Capítulo 2
3D
FEA
OF THE STRESS DISTRIBUTION WITHIN DIFFERENT METAL PLATESAND SCREWS AND INTERNAL FIXATION TECHNIQUES
,
IN MANDIBULAR ANGLE FRACTURES
75
2.1 Abstract
Purpose: Conduct a computational, laboratory-based comparison of the
mechanical stability of 2.0 non-compression plates made of commercially pure
titanium and a titanium-molybdenum alloy and two methods of internal fixation,
employed in favorable to displacement mandibular angle fractures, using 3D
finite element analysis.
Material and Method: A CT scan of a synthetic mandible was performed. After
the CT scan, the geometric model was reconstructed in Mimics 13.1. Then, the
file was reconstructed in a graphic design program (SolidWorks) and a simple
mandibular angle fracture, unfavorable for treatment, was simulated. The
samples were divided into 4 groups, according to the plate material and internal
fixation technique: group Eng 1P, one 4-hole plate and 4 screws 6 mm long, in
the tension zone of the mandible; group Eng 2P, two 4-hole plates, one in the
tension zone of the mandible and the other in the compression zone, the first
was fixed with 4 screws 6 mm long and the second with 4 screws 12 mm long.
The same groups were created for the titanium alloy (Ti-15Mo). The plates and
screws were modeled in the graphic design program SolidWorks and adapted
to the mandible. The finite element mesh and the numerical analysis were
performed using the finite element software, ANSYS Workbench 10.0.For the
computational simulation, a 100 N compressive load was applied to the occlusal
surface of the mandibular 1st molar on the plated side. The results were
analyzed considering the von Mises equivalent stress (σvM) for the plates and
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Results: When considering the von Mises equivalent stress (σvM) values for
the comparison between both groups (Eng and Ti-15Mo) with 1 plate, an
decrease of 10.5% in the plate and an decrease of 29.0% in the screws for the
titanium-molybdenum-based group was observed. Also, when comparing the
same groups with 2 plates the relevant fact was an decrease of 28.5% in the
screws for the Ti-15Mo group.
Conclusion: The titanium-molybdenum alloy plates substantially decreased the
stress concentration in the screws for both internal fixation techniques.
Keywords: Finite element analysis; mandible; fracture fixation, internal;
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2.2 Introduction
The treatment of mandibular fractures has been the focus of some
controversy due to the frequency of this trauma as well as the treatment
difficulty in healing a sensitive load-bearing region that is susceptible to
infection. These fractures most commonly occur in 20- to 40-year-old males as
the result of personal assault, falls, or motorized vehicle accidents (Gabrielli et
al., 2003).
In recent years, there have been many studies concerned with the
development of new bone-plates with appropriate mechanical properties to
improve fractured bone healing. Precise evaluation of the mechanical stresses
that develop in a fractured mandible is essential.
The literature includes two main ways to reduce stress shielding and
damage to the bone’s blood supply in the fractured bone. The first way is
modification of the bone-plate material. The second is reduction of the contact
between the bone and the plate. Little work has been done to investigate the
combined effects of these two parameters on stress shielding in the fractured
bone.
Various types of internal fixation devices like bone-plates are used to
promote bone structure stabilisation (Kim et al., 2010; Kharazia et al., 2010).
The bone-plates should be biocompatible and have the appropriate mechanical
properties for supporting the fractured bone (Kharazia et al., 2010; Uhthoff et
al., 2006; Lovald et al., 2009; Ramakrishna et al., 2004; Veerabagu et al.,
2003). Conventional bone-plates that are made of metals such as
